Development and psychometric validation of the Sexual Health Literacy Measurement Tool for Undergraduate Students (SHL-US) in Thailand

Background Sexual health literacy refers to an individual’s capacity and proficiency in managing sexual health. Currently, there are limited instruments available to assess sexual health literacy among undergraduate students, particularly in Thailand. Thus, the current study aimed to develop and psychometrically validate the sexual health literacy measurement tool for undergraduate students (SHL-US) in Thailand. Methods The study involved 1,235 undergraduate students from public and private universities in Thailand. A multi-stage probability sampling design was used, with simple random selection of institutions (one public and one private university per region, across four regions), faculties, and classrooms, followed by complete enumeration of eligible, consenting students within the selected classrooms. A pilot test (n = 50) and exploratory factor analysis (n = 300) preceded the confirmatory sample (n = 1,235). Thirteen experts examined the content validity. The quality of the instrument was tested by examining its psychometric properties using exploratory and confirmatory factor analyses. Results Forty-nine items entered the EFA; 47 were retained (4 factors, 53.17% variance explained). CFA removed two more low-loading items (<0.50), yielding the final 45-item, four-factor structure: access (12), understanding (12), appraisal (10), application (11). Additional internal consistency analysis yielded satisfactory results, with an overall Cronbach’s alpha coefficient of 0.976. The item-total correlation (ITC) was 0.284–0.755, and content validity, assessed via the content validity index (CVI), was high (CVI = 0.94). Confirmatory factor analysis, using the item set confirmed against the CFA diagram and retaining only correlated residuals with genuine item-content justification, supported an acceptable four-factor structure. The four domains were strongly inter-correlated, suggesting they are best interpreted and scored as facets of a single overarching SHL construct rather than fully independent subscales. Conclusion The SHL-US (45 items) showed acceptable four-factor fit and good internal consistency, though the four domains behave as correlated facets of one SHL factor rather than separable competencies. Used as a single overall score, it shows potential for assessing sexual health literacy among Thai undergraduates.